The research program of this laboratory is the study of protein- protein interactions which lead to the self-assembly of quaternary structures. The broad objective of these studies is to elucidate the nature of such interactions including the mechanisms by which the resultant subunit associations are controlled, and to obtain information concerning the physical characteristics of specific systems. Since the ultimate success of such a program depends on the continuing development of improved methodology for physical characterization of interacting protein systems, a primary concern of this research is the development and utilization of new techniques. The use of molecular sieve chromatography for studies of protein association equilibria at low concentration and the further development of this technique as an analytical tool for such studies are basic approaches of the program.